The normally chatty 50-year-old crouches behind a cluster of juniper trees and puts a finger to his lips. The four men behind him fall mute. Vader lies on his belly, points his rifle at the biggest bull and becomes part of a contentious experiment in controlling an icon of the American West.

Vader has one of 50 permits from Montana to kill a buffalo during the state's first legal hunt of the animal in 15 years. The quarry belong to a herd of 4,000 that roams freely in Yellowstone National Park, where hunting is banned. But winter snows chase them across the park boundaries into southern Montana, where they are not welcome.

The buffalo can carry brucellosis, a disease that causes cows to miscarry and that Montana views as a threat to its $1-billion cattle industry. The state confines the buffalo to a narrow slice of land, and chases them back to the park by helicopter and snowmobile should they venture too close to the few nearby ranches with cattle.

Sometimes the buffalo are killed; this year, about 500 have been herded into pens and slaughtered.

Montana officials and hunters hope the hunt can provide an alternative way of controlling the herd's movements. Most game animals -- including elk and antelope -- are managed by regulated hunts that keep herds at an optimum size, not so big that they will steal habitat from other species, but not so small that they risk extinction.

"It's more dignified for the buffalo to be hunted than to be put in trucks and hauled off to slaughter," said Terry Suhr, 49, a taxidermist who shot a buffalo the same day Vader was chasing one.

Environmentalists agree -- to a point. They have long decried the way Montana treats the buffalo.

"Yellowstone Park was started to protect the last buffalo ... and we're slaughtering them to protect animals that aren't even native to Montana," said Mike Mease, co-founder of the Buffalo Field Campaign, which monitors and protests Montana's treatment of the creatures.

Mease, 44, is a hunter who seeks to convert people like Vader to his cause, hoping to strengthen the alliance of environmental and hunting groups across the West that has helped preserve habitat for waterfowl and elk.

His group shadows the buffalo hunters, carrying an odd combination of recruiting brochures and objections -- they still oppose the hunt, arguing that it is "canned" because the buffalo are being treated like domestic animals in Montana, confined to a few thousand acres.

Vader and his hunting buddies have thought long and hard about these issues: Is it sporting to stalk a creature that is so oblivious to danger that, 125 years ago, millions were slaughtered by gunmen who could ride right into herds?

Buffalo, also known as bison, are found throughout the West but mostly live on ranches and are largely descended from cross-breeding with cattle. The Yellowstone herd is among the few herds that have no cross-breeding in their lineages and the only one that roams wild.

For several years until 1991, Montana's Department of Fish, Parks and Wildlife held hunts to control the buffalo. State wildlife agents would lead hunters to buffalo that ventured too far into Montana, then point out which ones they could shoot. They'd even provide a tractor to haul away each 1-ton carcass. Protests by environmentalists set off a national outcry, and the state canceled the hunt.

Gov. Brian Schweitzer, an avid hunter and former cattle rancher, said he was no fan of that approach.

When he approved the latest hunt, he said he wanted it to be a true sporting event. In Montana, he said, "we like to hunt. We're not people that put a bucket of grain behind our house so we can shoot an elk off our deck. We like to get out."

Even so, some hunters have been able to drive up and stand near the road to shoot the buffalo. Others have chased the animals, or, after wounding one, stalked it for miles to finish it off.

The governor acknowledged that buffalo would never be as difficult to hunt as more skittish animals. But he said he hoped they would develop a healthy fear of humans to make their pursuit more challenging, which would lead him to increase the number of buffalo hunting permits.

Schweitzer is also trying to persuade Yellowstone-area ranchers who have small herds of cows to move them so the buffalo can roam more freely in the state. That would end the need for the systematic herding of bison that last month caused a group of buffalo to flee onto an iced-over lake and fall in. Two drowned.

As the five hunters in the Vader party gather in the breakfast room of a Gardiner, Mont., motel at 6 a.m. on a recent Monday, they shake their heads and mutter regretfully about the drownings. Pictures of the mishap, taken by Mease's group, were splashed across newspapers over the weekend.